1. Field of the Invention
The present invention relates to a display using a Light Emitting Diode (LED) as a back light for a display, such as a Liquid Crystal Display (LCD), a projection TV, an Organic Light Emitting Diode (OLED) display, and more particularly to a method and an apparatus for providing additional information through a display by applying visible light communication to an LED used as a back light of the display.
2. Description of the Related Art
As luminous efficiency of LEDs improves, and the price of LEDs decreased, the LED has been generalized in general lighting markets, including fluorescent lamps, incandescent electric lamps and special lighting markets, including portable devices, displays, cars, traffic lights, billboards and the like. White LED has already surpassed incandescent electric lamps in terms of luminous efficiency, and white LED products superior to fluorescent lamps have recently emerged. Also, various factors, such as the exhaustion of RF bandwidth frequency, interference possibilities between several wireless communication technologies, an increasing demand for communication security, the advent of an ultra-high speed ubiquitous communication environment based on 4G wireless technologies, etc., have recently increased interest in optical wireless communication technologies complementary to RF technologies. Accordingly, research on visible light communication employing a visible light LED is now in progress by many enterprises and laboratories.
An LED has a color range similar to other conventional lighting sources, and thus its utilization in a display field has been further expanded. Accordingly, the LED is now used as a back light for an LCD, a projection TV, etc. The LCD has a more competitive power than a Plasma Display Panel (PDP) in terms of price, and its market has gradually expanded. Projection televisions have occupied the market for television displays over 50 inches. Also, in a computer monitor market, there is tendency that nearly all manufactured monitors are LCD monitors.
Meanwhile, as an element constituting a Back Light Unit (BLU) of an LCD TV changes from a Cold Cathode Fluorescent Lamp (CCFL) to an LED, a dimming technique for controlling the brightness of a backlight of the LCD has changed from a conventional global dimming technique for simultaneously turning on/off all of the lights of the BLU, to a local dimming technique.
In the local dimming technique, the BLU is divided into a plurality of areas, and brightness of each area is independently controlled. For example, in this technique, for an area corresponding to a dark part of a screen, the backlight is turned off, and for another area corresponding to a light part, brightness of the backlight is raised. This can significantly improve the contrast and the sharpness of an LCD, compared to conventional techniques.
However, when such a display device, such as an LCD, displays to-be-displayed contents, there is no method for providing additional information besides information displayed through the screen. In general only one component of display information can be delivered via a single display.